Monitoring who you talk to and about what is coercive control.
Expecting you to quietly soldier on - ie navigate managing a home/children alongside his disruptive/toxic behaviour - is a ‘hostage taking’ tactic. Keep quiet, or else etc. You must be exhausted.
The consequences of his unchanging behaviour has left him with ONE choice: do the right thing and leave quietly.
Otherwise you may well end up on SS radar - and that would be on him.
However, you sound like a caring and thoughtful mum, a bright soul whose light is clouded by the bullshit antics of your partner. He’s not on the same page, is he. You sound ready and willing for positive, proactive change.
Down but not out, OP, yes? Get him out of the house - the shift in dynamics will work wonders. Level playing field, renewed energy, vision and purpose as you start to rebuild your life.
Like other posters commented, support from his mum is not appropriate. It’s too loaded. You’ve got a lot going on - GET HELP from agencies/groups/individuals who have solid experience.
When I finally connected with meaningful support, I asked myself “What took me so long?!” But it is what it is for each of us - maybe ‘Now’ is the time for you?
Keep posting as you go into the new year x